Amino acid sequence of RS virus matrix protein was deduced from sequencing a recombinant plasmid containing a cDNA copy of this gene. The cDNA clone lacks about 10 nucleotides of the 5 feet end of the mRNA but the 3 feet end is preserved. There is one long open reading frame encoding 250 amino acids that presumably constitutes the matrix protein. There is also another open reading frame which overlaps with the long open reading frame. This second open reading frame encodes a protein of 75 amino acids. Whether the matrix protein gene actually produces an additional viral protein is being investigated. It should be noted that certain recombinant plasmids containing the matrix protein gene hybrid select viral mRNA(s) that yield upon translation the matrix protein and another protein that comigrates with a viral nonstructural protein (NS2). However, only an mRNA 1000 bases long hybridizes with this plasmid.